media: rkvdec: Stop overclocking the decoder

While this overclock hack seems to work on some implementations
(some ChromeBooks, RockPi4) it also causes instability on other
implementations (notably LibreComputer Renegade, but there were more
reports in the LibreELEC project, where this has been removed). While
performance is indeed affected (tested with GStreamer), 4K playback
still works as long as you don't operate in lock step and keep at
least 1 frame ahead of time in the decode queue.

After discussion with ChromeOS members, it would seem that their
implementation indeed used to synchronously decode each frame, so
this hack was simply compensating for their code being less
efficient. In my opinion, this hack should not have been included
upstream.

Fixes: cd33c830 ("media: rkvdec: Add the rkvdec driver")
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: Sebastian Fricke <sebastian.fricke@collabora.com>
Reviewed-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>